1. Ch1 Introduction Importance: 生物醫學－Blood flow； kidney stones； 溺水時急救
打氣等等……
工業 －引擎、汽車（運輸工具）流線造型、如聯
結車之整流罩等等……、或crude oil
across Alaska through an 800-mile-long，
4ft-dia. pipe、航空器、飛機氣動力學等等 ……
自然界 －大氣、海洋、火山爆發、地底岩漿、海岸
消蝕等等……
(Show Transparencies relating to Fluid Mechanics)
Solid & Fluid：What is a fluid?
From Observation－Solid (hard; not easily deformed);
Fluid (Soft; easily deformed; readily move through air)

2. From Scientific or Engineering Point View － Molecular structure of Materials (Solid vs. Fluid; intermolecular cohesive forces)
Thus liquids can be easily deformed (but not easily
compressed).
Gases：have even greater mlc spacing and freedom of
motion with negligible cohesive intermlc
forces; very easily deformed (and
compressed) and will completely fill the
volume of any container in which they are
placed.
A more specific distinction：
How they (gas, liquids, solids) deform under
The action of an external load.

3. Solid (within the limit of elasticity)
Shear stress shear modules shear strain
of elasticity
Fluid a fluid is defined as a substance that deforms
continuously when acted on by a shearing
stress of any magnitude.
plate
no slip condition
H bubble (velocity)
Dimensions, Dimensional Homogeneity, and Units (See the text books; Table 1.1; SI/BG)

4. Characteristics of A Fluid:
Density: (Greek symbol)
Specific volume:
Specific weight:
Specific gravity: S.G.=

5. unit vectors) Stress at point： tangential stress normal stress
Define：tension stress（+）
compression stress（-）
Fluid in static state

6. Viscosity: (Solid) shear stress ~ shear strain （ ）
(Fluid) shear stress ~ time rate of shear
strain（ ）
（absolute viscosity）
（kinematic viscosity）

7. Time rate of strain
（angular deformation） 1. 2.

8. Velocity gradient change of velocity in x-direction in Y plane.
(SI)
(BG)
An important parameter
for momentum transport
(Contact area per second)

9. Ideal gas law：
Non-ideal gas：
Compressibility of Fluids：
Bulk Modulus
Isothermal bulk modulus of elasticity
Coefficient of compressibility

10. Compression and Expansion of Gases：
Isothermal process：
Isentropic process：
（no heat exchanged with the surroundings）
Speed of sound
Isentropic process (small disturbances more
rapidly negligible heat transfer)

11. Vapor Pressure
Some liquid mlc at the surface
have sufficient momentum to
overcome the intermlc cohesive
forces and escape into the
atmosphere.
pressure is called vapor pressure
Appendix B（Tables B.1 & B.2）
Boiling：which is the formation of vapor bubbles within
a fluid mass, is initiated when the absolute pressure in the
Fluid reaches the vapor pressure

12. Sea Level：
T P
water boiling 100。C （212。F） 1atm（14.7psi）
10,000ft：
water boiling 89.4。C （193。F） 1atm（10.1psi）
Cavitation：1.underwater explosion
2.Ship propeller
3.Irregular, narrowed passages of a valve
or pump
cause structure damage

13. Surface Tension
a liquid/ a gas or between two immiscible liquids,
forces develop in the liquid surface－skin.
ex：a steel needle will float on water if placed on the
surface.
and other fluids
The difference between the
pressure inside the drop and
the external pressure
The pressure inside the drop＞the pressure
surrounding the drop

14. Continued Surface tension
Q: Would the pressure on the inside of a bubble of
water be the same as that on the inside of a drop of
water of the same diameter and the same temp?
Fig.1.7 Effect of capillary action in small tubes.
Liquid-gas-solid interface
liquid wet solid surface
wetting
Q－angle of contact

15. Mercury
Non wetting
＊give some example from NCFM
Inertial,gravitational&viscous process are much more